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Growth hormone response to growth hormone-releasing peptide-2 in growth hormone-deficient Little mice

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Autor(es):
Peroni, Cibele N. ; Hayashida, Cesar Y. ; Nascimento, Nancy ; Longuini, Viviane C. ; Toledo, Rodrigo A. ; Bartolini, Paolo ; Bowers, Cyril Y. ; Toledo, Sergio P. A.
Número total de Autores: 8
Tipo de documento: Artigo Científico
Fonte: Clinics; v. 67, n. 3, p. 8-pg., 2012-01-01.
Resumo

OBJECTIVE: To investigate a possible direct, growth hormone-releasing, hormone-independent action of a growth hormone secretagogue, GHRP-2, in pituitary somatotroph cells in the presence of inactive growth hormone-releasing hormone receptors. MATERIALS AND METHODS: The responses of serum growth hormone to acutely injected growth hormone-releasing P-2 in lit/litmice, which represent a model of GH deficiency arising frommutated growth hormone-releasing hormone-receptors, were compared to those observed in the heterozygous (lit/+) littermates and wild-type (+/+) C57BL/6J mice. RESULTS: After the administration of 10 mcg of growth hormone-releasing P-2 to lit/lit mice, a growth hormone release of 9.3 +/- 1.5 ng/ml was observed compared with 1.04 +/- 1.15 ng/ml in controls (p<0.001). In comparison, an intermediate growth hormone release of 34.5 +/- 9.7 ng/ml and a higher growth hormone release of 163 +/- 46 ng/ml were induced in the lit/+ mice and wild-type mice, respectively. Thus, GHRP-2 stimulated growth hormone in the lit/lit mice, and the release of growth hormone in vivo may be only partially dependent on growth hormone-releasing hormone. Additionally, the plasma leptin and ghrelin levels were evaluated in the lit/lit mice under basal and stimulated conditions. CONCLUSIONS: Here, we have demonstrated that lit/lit mice, which harbor a germline mutation in the Growth hormone-releasing hormone gene, maintain a limited but statistically significant growth hormone elevation after exogenous stimulation with GHRP-2. The present data probably reflect a direct, growth hormone-independent effect on Growth hormone S (ghrelin) stimulation in the remaining pituitary somatotrophs of little mice that is mediated by growth hormone S-R 1a. (AU)

Processo FAPESP: 01/11091-0 - Modelos animais de terapia gênica: estudo da expressão prolongada do hormônio de crescimento em camundongos anões (little/little) e anões imunodeficientes (little/scid)
Beneficiário:Paolo Bartolini
Modalidade de apoio: Auxílio à Pesquisa - Regular
Processo FAPESP: 09/15386-6 - Análise dos genes CDKN1A, CDKN1B, CDKN2B e CDKN2C, nas neoplasias endócrinas múltiplas tipo 1 e 2.
Beneficiário:Rodrigo de Almeida Toledo
Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado